The present invention relates to a clamping ring (otherwise known as a clamp) of large size, particularly intended, by clamping, to hold a rigid or flexible oil duct or a similar heavy cylindrical elongate element (tube, cable, umbilical) and which is designed, in particular, to be used in a device for laying tubular ducts under water from a laying vessel.
French Patent Application No. 98/00148 in the name of the Applicant Company, to which reference can usefully be made, and the teaching of which is incorporated herein by reference, discloses a duct-laying device of the family of J-lay devices. It comprises an inclinable tower, placed in and a great height above the moon pool of the laying vessel, and designed to take a certain length of duct that is to be laid, and means for holding and shifting the said length of duct; the said means comprise two motorized mobile carriages capable of travelling the said height of the tower, and able to take members for holding the duct. These holding members are very advantageously clamping jaws (otherwise known as clamps), that is to say actual (and static) clamping devices, as opposed in particular to linear caterpillar-type tensioners (which entail moving the duct along at the same time as the clamping jaws) By controlling the tightening of the clamps and the displacement of one or other of the carriages along the tower, it is possible to use the device described in the aforementioned application in a great many possible configurations, giving the device great versatility, in order to move the duct along in what is known as the hand over hand fashion.
Document GB 2,299,646 discloses a clamp with jaws borne by connecting rods in the form of an articulated parallelogram, in accordance with the preamble of the appended Claim 1. However, in this device which is intended to keep a duct horizontal, the movement of the jaws is essentially longitudinal and is ill-suited to the problem at which the invention is aimed, namely that of holding heavy vertical ducts.
The object of the invention is to provide a clamp which is particularly well suited to this context.
The object of the invention is achieved by virtue of an annular clamping ring comprising a rigid annular base which has an axis, and supporting, by support means, a coaxial ring-shaped assembly of jaws parallel to the axis and mobile in diametral planes, the said support means comprising, on the one hand, a rigid annular body surrounding the assembly of jaws, mobile in axial translation by means of controllable cylinder actuators which connect it to the base, the jaws being connected to the annular body by at least two connecting rods forming an articulated parallelogram, characterized in that the said support means also comprise long connecting rods articulated on the base and on the outside of the jaws in a position which is almost the axial direction, such that the axial translation of the annular body with respect to the base causes a substantially radial and synchronized displacement of the assembly of jaws.
Advantageously, each of the jaws consists of a main jaw which consists of a main beam and of a secondary jaw which consists of an adapter girder mounted on the main beam at a distance away that can be altered between at least two positions, which makes it possible to increase the range of duct diameters that can be accommodated. As a preference, the adjustment of the distance may differ from one girder to the next or from one group of girders to the next, so that a lower number of girders can be used for ducts of small diameter.
This diversity is further enhanced if the adapter girders are chosen from sets of several sizes.
Advantageously, provision is made in the base and the body of the clamp for a sector, thus constituting a doorway which can advantageously be locked, for slipping a duct in sideways or for inspection.